A focused ion beam (FIB) apparatus for performing etching processing and microscopic observation has been known.
In the focused ion beam apparatus, in general, when a sample is processed, the sample is irradiated with an ion beam having a large current amount, to thereby subject the sample to etching processing. On the other hand, when the sample is observed, the sample is irradiated with an ion beam having a small current amount in order to reduce the etching amount of the sample and reduce the beam diameter, and then secondary charged particles generated from the sample are detected to perform microscopic observation of the sample.
Further, in the focused ion beam apparatus, in general, the current amount of the ion beam to be radiated is changed depending on the processing rate and accuracy. To change the current amount, it is necessary to change the settings of ion beam optics. For example, there is known an ion beam apparatus in which conditions of ion beam optics for different current amounts are stored, and at the time of beam switching, corresponding optics conditions are read and set to the optics (see JP-A-H10-106474).
According to this apparatus, in the case of switching between ion beams having different current amounts, the optics conditions can be switched smoothly.
In the FIB apparatus, in order to set an irradiation position when performing fine processing, the sample is observed at a high magnification. On the other hand, in order to check the position of a processing target, it is also necessary to observe the sample in a wide range, and hence the sample is sometimes observed at a low magnification. In this case, beam switching is performed in a manner that the apparatus stores in advance the optics conditions for a wide-range observation mode where the sample is scanned and irradiated with the ion beam in a wide range. For the beam switching, it is necessary to switch the voltage to be applied to a lens electrode of the optics.
However, there is a problem in that, in the case where the voltage to be applied to the lens electrode of the optics is switched, if a high voltage is abruptly applied to the lens electrode, discharge is generated. Accordingly, the beam switching to apply a high voltage needs to be performed so that the voltage is increased gradually so as not to generate discharge. Thus, there has been a problem in that it takes time for the beam switching to be performed.